Speaking to reporters in Washington on Monday, Nebraska Sen. Ben Sasse said his state's Republican activists had failed to represent Americans, adding that Republican voters were "dying" and that the party had "exited the playing field."

The comments came after a weekend convention at which the state's Republican delegates voted almost unanimously to condemn Sasse for saying that he would refuse to support the party's presumptive nominee, Donald Trump.

"I have lots of respect for grassroots activists in the Republican Party in the state who've built a really good state Republican Party," Sasse said Monday evening. "Nebraska is a really well-governed place because we have a lot of hard-working people at the local level.

"That said, I don't really spend any time on short-term issues like a resolution at one convention meeting, because the people who are at that are not necessarily representative of what most Americans think and what most Nebraskans think," he said, adding that he believes it was "pretty obvious" that voters "wish they had better choices … [and] a big optimistic conversation about the future of the country."

The remarks came after a speech Sasse delivered at an event sponsored by the American Enterprise Institute. The first-term senator suggested that traditional Republican voters were not long for this world and added the party should do more to appeal to impoverished voters.

"Demographically, the middle class really is shrinking," Sasse said. "I'm part of a political party that doesn't like to admit this very much. Democrats regularly act like any problem … it's tinkerable … But then you look at my party and you say what are we offering instead, we don't have much of a vision for young people. We don't have much to offer that's optimistic and persuasive about where we're headed."

"The party that I'm a part of is largely suffering from a declining customer base, because root, sort of core Republican voters are dying," Sasse said. "The Democrats don't have the same customer base problem, but they have a massive product problem, because the Democrats are still trying to pretend that if you just try to expand 1965 entitlement programs … that somehow you're only three tinkers away from being a working system."

"We have a political playing field that has one party that seems to want to make Washington more powerful in trying to centrally plan things, and another party that looks like we've largely exited the playing field," Sasse added.